Re: Tektronix 564 WW resistor for -100V supply

Trevor
 

The choice of wire-wound was probably for temperature stability of the -100 volt power supply. Since R617  forms a voltage divider with pot R616 and R618, both also specified as wire-wound, the circuit designer wanted resistors with tracking temperature coefficients. The 1% spec is superfluous. You could use any resistor type, but you would compromise temperature stability if the three resistances don't track. If you use a carbon-composition resistor as a replacement, say 82K, consider changing R618 to carbon-composition as well. Then see how the -100 volt supply behaves as the scope heats up.

An RN65 78.7K metal film resistor is probably a better choice, however.

-Trevor

On Thursday, May 23, 2019, 10:22:08 PM EDT, Brenda via Groups.Io <brendda75=yahoo.com@groups.io> wrote:

HI everyone! I thought I would take my 564 out and see what I possibly do to get the storage section of the CRT working again.  I fired up the scope and only to find that absolutely nothing worked. I measured all the low voltage supplies and they are all severely off.  The -100V was reading -77, and with that, decided to check everything in the -100V circuit.  All of the resistors were still in tolerance except for R617 which is an 80K WW 1W resistor and it was completely open.  The brand of the resistor is Reon. I am wondering if any 80K resistor would work in it's place as long as the wattage is greater than 1W and is within the 1% tolerance spec? Or does it have to be a WW resistor?

Brenda

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